9 replies to this topic

[DrWeird]

So I've jumped into it, and devac'd my car, a 1984 1.5 Civic. The problem before was rampant vacuum leaks, broken emissions systems, etc, which made the car un-drivable to the point where it would not idle when cold, and had to be held manually above 2000rpm to run (smoking wildly) at all times.

During the devac I found even more vacuum leaks, and am enjoying the streamlined engine bay.

I also opted to maintain the air-control system, as mentioned later in the devac sticky thread.

But, that being said, the work is not done. I am looking for a bit of help/diagnosis.

One question: the multi-valve looking things on the back bottom of the intake manifold (many small vacuum connections coming off, then say, 1/2" lead into the manifold on the other side), should I block these off? They are currently open (all the little connections). Also, is there an available bung to block the entire thing (say from ACE or someplace)? If so, could I get a name or part number?

The car runs currently as follows: idles very high when warm, and sputters/pops all the time. The thing has maybe 30% exhaust left and no muffler thanks to the rust gods, so its top-fuel dragster loud, with almost no exaggeration. The thing is louder than most huge diesel trucks at full tilt. I'm thinking the issue may be too much fuel/vacuum leaks from the open ports I mentioned beforehand. Is this correct in idea? Some things I've already looked at is that there are no other vacuum leaks except maybe at the insulator (big rubber brick), and the carb was rebuilt at some point in the past year or two, and seems ok. Its not flooding out, doesn't smell like gas or smoke, and the float is working and set at the correct level.

Also, I think its only getting ~30mpg, which is a bit low from my experience with this car. Any insight would be appreciated

[Bubba]

There is no need to remove/block the thermostatic vacuum valves on the lower rear end of the intake manifold, they may look ugly but they will not leak any vacuum.

[DrWeird]

There is no need to remove/block the thermostatic vacuum valves on the lower rear end of the intake manifold, they may look ugly but they will not leak any vacuum.

Thanks, that's what I thought, but couldn't convince myself for sure.

So in terms of reducing fueling/idle speed, any hot tips for devac'd cars? I've not messed with the mix screw, since I hear that's a can of worms best left un-opened. Any other way to modulate this? What is the easiest way to check the mix is correct? Wide-band install, or something else? The idling at 3k is what really bothers me.

[Bubba]

It could possibly be that part of what you devaced was the fast idle and choke pull off- it sounds like you are stuck in fast idle mode. You can hook a single vac line to the choke pull off and that will probably save a little gas (pull off the choke faster at startup) and might also help your high idle problem.

[DrWeird]

It could possibly be that part of what you devaced was the fast idle and choke pull off- it sounds like you are stuck in fast idle mode. You can hook a single vac line to the choke pull off and that will probably save a little gas (pull off the choke faster at startup) and might also help your high idle problem.

I suppose I will hook that up to a thermostatic valve in order for the pulloff to not be on all the time. The weird part is that the car idles at 1000-1500, but roughly, when cold, and once it runs ok and has power when warmed up, it sits at 3000-3500. I've tied the primary and secondaries together, perhaps this is the issue? I'm thinking the mix is just off somehow.

With the devac, the electric choke doesn't really work, does it? Perhaps I should rig up a way to turn on/off the electric choke?

[Bubba]

As long as you still have the wire that goes to the choke plugged in, the electric choke does still work- it just opens really slowly as the engine warms up. The choke pull off does operate on vacuum and opens the choke a little bit as soon as the engine starts.

Maybe the engine is missing on one cylinder when it is cold and when it hits on all 4 (when warm) the idle is really high- you can check this by taking the spark plugs loose one at a time and seeing if the idle drops.

Another possibility is that if the secondary butterfly sticks open even a tiny crack, it will idle really high.

[kaymo]

yeah i had to add a chevy carb spring to mine to keep it closed to idle. just try jamming it back by hand. if idle drops, there you go

[DrWeird]

yeah i had to add a chevy carb spring to mine to keep it closed to idle. just try jamming it back by hand. if idle drops, there you go

Alright, I'll try slamming it back. It once had an issue with the accelerator not resetting all the way, so I extra-wound the return spring on the carb, but maybe that wasn't enough.

I will also hook up the pull-off. Thanks for the info on the electric choke, its still hooked up, I just haven't stood around and watched it do its thing, so I wasn't sure it worked.

Thanks for the info, and I'll give it a look this weekend.

[kaymo]

yeah the rewind didnt work for me, so i just added another light spring. super heavy pedal but great for modulating gas for "eggfoot" mpg driving

[yogmuney]

yeah the rewind didnt work for me, so i just added another light spring. super heavy pedal but great for modulating gas for "eggfoot" mpg driving

You should make sure that the choke is set so that it opens all the way up once it is warm or you will get crappy mileage.